The reference coplanar 106-day GJ 876 test object escapes after a close approach to planet c

We test a physical interpretation of a 106.1076-day GJ 876 velocity signal from a prior SCI HARPS survey. The reported Keplerian curve has eccentricity 0.7546 and velocity semiamplitude 3.7081 m/s. We add its coplanar, prograde orbit to a published four-planet system at BJD 2455000. All six bodies then interact under Newtonian gravity. In the reference model, the added object passes within 0.005 AU of planet c after 2.044 years. A separate continuation reaches 10 AU after about 3.4924 years. The object moves outward with positive orbital energy relative to the remaining system. Its outward speed is about 3.75 times the local escape speed. Three numerical precision settings give the same escape outcome. A fixed 87-run design tests known-orbit rows, candidate phase, eccentricity, mass, coordinate origin, and period. It records 78 close approaches, eight escapes, and one 10 AU stop with negative energy. Every case stops within 58.59 years. These are design counts, not planet probabilities. All 17 four-planet controls avoid the distance threshold for 100 years. The package contains source rows, source hashes, complete Cartesian initial states, results, figures, source code, and reproduction instructions. This is a conditional dynamical test, not a joint fit of five planets or a complete orbit posterior. A close approach alone is not a collision or proof of escape. The test object does not remain on a bound orbit in the reference model. The result does not explain the observed signal or exclude all additional planets.

GJ 876 · radial velocity · planet dynamics · candidate validation · HARPS-RVBank · close approaches · planet escape · reproducible benchmark